1. Desalination and Reverse Osmosis Koh Huai Ze (10)

2. What is Desalination? O The process of removing salt and other minerals from water O Water is desalinated in order to convert salt water to fresh water so that it is suitable for human consumption O Very costly as it requires large amounts of energy and specialised infrastructure

3. Methods of Desalination Vacuum Distillation O The boiling of water at a much lower temperature than normal, saving energy Reverse Osmosis O Uses membranes to desalinate, applying reverse osmosis technology O Uses semi-permeable membranes and pressure to separate salts from water O Less energy is used compared to thermal distillation O Also used to purify fresh water for medical and industrial uses

4. Reverse Osmosis Desalination Plant

5. Reverse Osmosis In normal osmosis: O Water molecules move from a region of higher concentration to a region of lower concentration through a partially permeable membrane In reverse osmosis: O Water molecules are forced to move from a region of lower concentration to a region of higher concentration by applying a huge amount of pressure

6. Reverse Osmosis Result: O The solute is retained on the pressurised side of the membrane O The pure solvent is allowed to pass to the other side Membrane used: O Designed to only allow water molecules to pass through O Does not allow larger molecules such as salt ions to pass through

8. Hope you have learnt something from this

9. The Process

10. Flow at the Membrane

11. The Process

12. Flow at the Membrane

13. An Overview of Desalination Processes In order to produce freshwater from salt water a suitable separation process must be devised. The task can be accomplished in many different ways, all of them based on the principle that water and salts do not separate spontaneously, and thus require some kind of energy source to power the separation process. The first desalination units used for freshwater production were based on the evaporation of pure water via the addition of heat provided by the sun or by combustion processes. In recent years, the development of modern polymer materials has led to the production of membranes which allow the selective passage of water (semi-permeable membranes) or ions (ionic exchange membranes), thus providing the basis for membrane desalination processes. Dr. Ola Abdelwahab 13

14. Membrane Processes A membrane is a selective barrier that permits the separation of certain species in a fluid by combination of sieving and diffusion mechanisms Membranes can separate particles and molecules and over a wide particle size range and molecular weights

16. Membrane Processes Four common types of membranes: Reverse Osmosis Nanofiltration Ultrafiltration Microfiltration

18. An Overview of Desalination Processes In order to produce freshwater from salt water a suitable separation process must be devised. The task can be accomplished in many different ways, all of them based on the principle that water and salts do not separate spontaneously, and thus require some kind of energy source to power the separation process. The first desalination units used for freshwater production were based on the evaporation of pure water via the addition of heat provided by the sun or by combustion processes. In recent years, the development of modern polymer materials has led to the production of membranes which allow the selective passage of water (semi-permeable membranes) or ions (ionic exchange membranes), thus providing the basis for membrane desalination processes. Dr. Ola Abdelwahab 18

19. Membrane Processes A membrane is a selective barrier that permits the separation of certain species in a fluid by combination of sieving and diffusion mechanisms Membranes can separate particles and molecules and over a wide particle size range and molecular weights

21. Membrane Processes Four common types of membranes: Reverse Osmosis Nanofiltration Ultrafiltration Microfiltration

23. Distillation

25. Treated water will then be transfer to the tank in Lodi where it is distributed to the costumers.